Analysis of the pathway of L-tryptophan biosynthesis has been valuable for the study of the relationship of genes and enzymes. Much is known about the pathway enzyme particularly in the Enterobacteriaceae, the bacterial family that includes Escherichia coli. However, the three dimensional structure of none of the enzymes is available. Our first objective is to try and obtain a crystal suitable for X-ray diffraction of one of the pathway proteins irrespective of whether the amino acid sequence is known. We have begun by purifying the enzyme, anthranilate-5-phosphoribosylpyrophosphate phosphoribosyltransferase from the bacteria Beneckea harveyi, Serratia marinorubra and Serratia marcescens. The enzymes are now under crystallization study. We will add additional enzymes of the pathway as they are purified. We are also obtaining the amino acid composition, about 10 amino acids of the sequence from the N-terminus, antigenic and enzyme characteristics of these enzymes in order to study their evolution within the bacterial family Enterobacteriaceae.